Mercury switch



Oct. 29, 1940. J. H. sTALY MERCURY SWITCH F'il ed Aug. 8, 1938 8 v z 4 m m mML W 3 V0./. 2 o 3 we 2 ,9 if m J5 Patented Oct. 29, 1940 UNITED STATES MERCURY SWITCH Joseph H. Staley, Columbus,- Ind. Application August 8,1938, Serial No. 223,624

2 Claims.

,This invention relates to the art of mercury switches and has for a primary object the provision of adequate hermetic sealing means in a metal wall tube employed in conjunction with a fragile arc resisting member and a metal electrode to be carried in an insulated manner by the tube. A further primary object of the invention is to provide such sealing means to serve also as a means for' locating and maintaining in position the arc resistingmember in its proper relationship with the insulated electrode.

These and other objects and advantages of the invention will become apparent to those versed in the art in the following description of the invention as illustrated in the accompanying drawing, in which Fig. l is a diametrical longitudinal section through a structure embodying the invention;

Fig. 2, a transverse section on the line 2-2 in Fig. 1;

Fig. 3, a diametrical longitudinal section through a modified form of the structure; and

Fig. 51, a transverse section on the line &t in

Fig. 3. I

Like characters of reference indicate like parts throughout the several views in the drawing.

Referring first to that form of the invention as shown in Figs. 1 and 2, a metal tube It is 30 formed by any suitable means such as by boring or by spinning or pressing the tube into shape to have in the case of a single circuit, as herein illustrated, a closed end and an initially open end;

The tube I is provided with an annular shoulder 1 H against which may be placed the inner end of an arc resisting member l2, hereinafter termed a breaker. The breaker n has an external cylindrical surface which will permitthe breaker to be inserted through the open end of the tube Ill and carried against the shoulder H. The diameter of the breaker 12 is made to be such that the breaker may be freely inserted within the tube and yet fit rather closely so as to prevent any normal flow of mercury between the outside of the breaker and the tube wall.

The breaker I2 is provided with a central bore therethrough which varies in shape as it transverses the breaker. As indicated in Fig. 1, the

- rear end of the breaker l2 has this bore opening at substantially over the entire area. From this large rear end opening, the bore is tapered toward the axis to form the conical part l3 of the bore. Then the bore is carried a short distance incylindrical form, which part is designated by the numeral M. The length of this cylindrical portion is short in comparison to the total length of the bore. The outer end of this short length It opens into a larger diameter bore part I5 and this part IS in turn initially opens into a still larger part It in the nature of a counter-bore.

A suitable quantity of mercury I1 is placed in the tube Ill and then an electrode I8 is entered by its head I9 into the tube It] to have this head 19 enter the counterbore l6 and thus form a wall across the outer end of the cylindrical bore part l5. The head I9 is cylindrical in shape and has an external diameter as will permit it to enter freely within the counterbore' it.

A resilient plug 20 made of any suitable electrical insulating material and having a central hole therethrough toreceive the stem of the bolt I8 is then entered into the open end of the tube It to have the bolt stem extending therethrough. The plug 20 is arranged to fit'closely around the outer or under side of the bolt head I9; and to come into engagement with the outer end of the breaker I! which is not covered by the head it. A second insulating piece 2| is also slipped over the stem of the bolt l8'to enter within the tube l0 and then the outer end of the tube in is turned over, such as by a spinning process, to form a flange engaging over the outer face of the plug 'part 2|. While the two parts 2|] and 2t may be made in an integral form, it is possible to make the. part 20 out of a more resilient material such as rubber or a synthetic rubber and to make the additional part 2| out of a harder material such as a-synthetic resin or vulcanized paper, in order that the end of the tube may be more readily turned over as the retaining means.

The bolt I8 extends sufliciently far from the end of the tube III as to serve as a terminal and may be screw-threaded, as indicated, to carry the nuts 22 and 23. A spacing washer 2% may be employed to, carry the inner nut 22 outwardly sufficiently far from the end of the tube Ill as to prevent any accidental short circuiting.

It is to be noted that in addition to the turning over of the outer end of the tube I ll as a means of compressing the plug inwardly against the bolt head and breaker to effect the seal by pressing the plug material outwardly'against the wall of the tube as well as inwardly against the headand breaker, the nut 22 by being turned on the threaded end of the'bolt I8 will further serve as a means in co-operation with the head I9 01 compressing the plug material laterally against the tube wall and also to cause it to flow out around the outer edge of the head Hi to efiect a tight seal between the breaker l2 and the head l9 so as to prevent leakage of mercury, particularly in the vapor form, between the inside of the breaker and along the face of the head to the tube wall.

Referring now to the other form of the invention as illustrated in Figs. 3 and 4, the same type of tube I0 is employed in that it has forv the single circuit a 'closed end and an open end and is also provided with an internal annular shoulder l-l.

, In this form however a modified form of breaker 24 is shown in that it has instead'of the conical e tube I to be entered from its open end and to becarried inwardly to abut the shoulder I! in the manner as shown in Fig; 3. A quantity of mercury I! is placed in the tube It. An electrode is formed in the nature of a bolt 28 which has a head 29 hollowed outin cylindrical form to form an opening entering the head of a diameter exceeding that of the boss 21 so that the electrode 28 may be entered through the open end of the tube ID to have the head abut the outer end of the breaker 26 with the boss 27 entering the opening in the head 29. The depth of the opening in the head 29 is arranged in respect to the length of the boss 27 so as to leave a space between the outer end of the boss 21 and the closed end of the bore in the head 29 sufficient to permit the mercury to flow between those two parts and around the periphery of the boss 21 in contact with the cylindrical wall of the hole in the bolt head 29. The spacing of these parts is determined by a number of factors, such as the limit of opening through which mercury will flow, retention of a suflicient quantity of mercury for a rated current capacity flow through the mercury, and the prevention of spill-over after current has been interrupted upon initial flow of mercury.

Since the bolt 28 and its head 29 is made out of a conducting material to serve in the capacity of an electrode, an insulating plug is employed to space it from the wall of the tube l0. While this plug may be made out of a single unitary piece of insulating material, it is herein shown as consisting of a sleeve 30 which surrounds the periphery of. the head 29 and a second piece 3| which surrounds the stemof the bolt 28 to fit against the inside wall of the tube In and against the outer or under side of the head 29. form, the outer or under side of the head 29 is shaped to be conical and a conical insulating member 32 engages about the stem of the bolt 28 to bear against the outer end of the plug piece 3|. A flanged collar 33 screw-threadedly engages over the outer sideof the open end of the tube ID to have its flange bear against the insulating member 32 as a means of compressing the plug member 3| in order to urge it laterally as well as inwardly to effect a seal about the electrode bolt 28, its head 29, and-the inside wall of the tube l0. Additional pressure is obtained by tightening a nut 22 on the screw-threaded stem of the bolt'28. The plug parts may be made out of any suitable insulating material which is at least slightly re- =silient in order to permit suflicient distortion to efl'ect the seal as indicated. The member 32 may be made out of the same material as are the plug parts, but preferably it is made out of a material slightly harder in nature in order that it will not be unduly distorted when it is compressed against the plug part 3 I.

Both forms of the invention may be operated by longitudinal tilting to cause the mercury to flow through the respective breaker bores to have- In this I tact therewith.

the mercury interconnect through those bores the tube Ill and the electrode head to complete the electrical circuit between those members. Tilting in the other direction will break the circuit by reason of the mercury I! being broken through the bore of the breaker.

It is obvious that various parts of .one form of the invention may be interchanged with similar parts in the other form, such as interchange of the electrodes; interchange of breakers; interchange of plug parts; or interchange of the compression means such as substituting the screwthreaded sleeve 33 for the turned over flange of the tube H1 in Fig. 1. Therefore, while I have herein shown and described my inventionin those two particular forms, it is obvious that structural changes may be made therein without departing from the spirit of the invention, and I, therefore, do not desire to be limited to those precise forms beyond the limitations as may be imposed by the following claims.

I claim:

1. In a mercury switch, a hollow metallic tube, a shoulder on the inside of the tube, a quantity of mercury, a breaker entered in the tube to abut said shoulder, an electrode having a stem and a head, .said head being entered in the tube into contact with the breaker, said breaker having a bore therethrough of at least two different diameters, the larger diameter part being and opening out at that end of the breaker which abuts said shoulder, said head having a diameter greater than the diameter of said lesser bore part in said breaker whereby the outer peripheral portion of the head bears against the breaker to leave a central area exposed to flow thereagainst of mercury through said bore, a resilient insulating plug around said stem and abutting said head, and means compressing the plug into sealing contact with said tube, stem, head and breaker and maintaining said breaker against said shoulder, said head carrying a counterbore to form a mercury receiving chamber therein in conjunction with said breaker, and a boss extending from the breaker into said chamber to leave a mercury flow space thcrearound, said bore continuing and opening outwardly through said boss.

2. In a mercury switch, a hollow metallic tube, a shoulder on the inside of the tube, a quantity of mercury, a breaker entered in the tube to abut said shoulder, an electrode having a stem and a head, said head being entered in the tube into contact with the breaker, said breaker having a bore therethrough of at least two diiierent diameters, the larger diameter part being and opening out at that end of the breaker which abuts said shoulder, said head having a diameter greater than the lesser diameter of said bore whereby the outer peripheral portion of the head bears against the breaker to leave a central area exposed to flow thereagainst of mercury through said bore, a resilient insulating plug around said stem and abutting said head, and means compressing the plug into sealing contact with said tube, stem, head and breaker and maintaining said breaker position, that portion of the breaker carrying the smallerdiameter bore having an external diameter less than that of the other portion, said electrode head having a cupped portion into which said breaker smaller portion extends withoutcon- JOSEPH H. STALEY. 

